1. Field Of The Invention
This invention relates to rollers mounted rotationally on bearings by means of ferrules, such as rollers designed to support a load that moves on a series of identical rollers mounted side by side. This load can include a strip material, such as a sheet of steel or a plate of glass.
2. Description Of The Prior Art
Rollers designed to support a metal strip are known, particularly in a heat treatment furnace in which the strip is annealed at a relatively high temperature. Such rollers are typically formed of a cylinder of refractory material and a ferrule rotationally mounted on a bearing is fixed at each end of the cylinder.
U.S. Pat. No. 4,399,598 discloses a ceramic roller for transporting glass sheets in a heat treatment furnace. The cylinder is mounted rotationally on bearings by means of ferrules mounted with play at each end of the cylinder. One or more split, circumferentially expandable, radially compressible metal rings are located in the space between the outside diameter of the cylinder and the inside diameter of the ferrule where the ferrule overlaps the cylinder.
Another known roller includes a cylinder of refractory material having metal ferrules affixed at each end. Play is provided between the ferrules and the cylinder and longitudinal metal platelets are embedded in this area of play.
These known systems of the prior art make it possible for the roller to take up differential dilatation during a temperature change. In effect, the cylinder of refractory material expands very little or not at all, while the metal ferrules expand greatly. As a result, the play between the cylinder and the ferrules varies substantially as a function of the temperature. It becomes necessary to provide elastic devices for taking up the variation in the play between the cylinder and the ferrules.
Nevertheless, these known arrangements have the disadvantage of not assuring that the ferrule and the cylinder remain coaxial under load. In effect, when the cylinder is supporting a load, the elastic devices, whether the split rings of U.S. Patent No. 4,399,598 or the longitudinal metal platelets, are deformed so that the ferrules are displaced angularly with respect to the axis of the cylinder.
It is an object of the present invention to provide a roller, including a cylinder and at least one ferrule mounted at the end of the cylinder, which overcomes this disadvantage of the prior art and will take up diametrical play while the cylinder and ferrules remain in coaxial alignment.